This invention relates to an apparatus for relieving muscular tension at a work station which requires use of one's hands or feet. More particularly, it relates to an apparatus for use in conjunction with a computer or other keyboard to prevent the operator from having excessive upper body tension as well as in conjunction with other instruments where arm support during hand assembly or control panel use is found to be an aid.
Application to Keyboard Operations
Operators of business machines, such as word processors, computers and typewriters often find muscular tension in the back, neck and arms because the arms must be elevated and suspended over the keyboard. Furthermore, often the operator will remain unconsciously tensed in the ready position even though he is not entering data. This is motivated by the wish to keep the fingers in constant reference to special keys on the keyboard. When this happens for a prolonged period of time, the discomfort of muscular strain can occur during work and lasting afterwards. Furthermore, when there is muscular tension, it is common for the operator to make errors. To alleviate this, a large number of work breaks is required in order to relieve the muscular tension.
Various devices have been developed for use in conjunction with a keyboard enabling the operator to rest his hands or arms while operating the keyboard. Some of such devices are disclosed in U.S. Pat. Nos. 4,482,063; 4,481,556; 4,482,064; 3,300,250; and 1,801,669. However, all of the devices disclosed in the above-referenced U.S. Patents are static; therefore, there will be an amount of friction between the person's arms and the contacting surface of the device when sufficient movement of the hands across the keyboard in the horizontal plane is attempted. Such movement of the hands calls for a momentary lift of the arms from the surface to avoid variations in friction which can suddenly release or bind depending on skin moisture, adhesion, and the texture of the surface.
A further problem arises in the use of cursor control devices which are either not on the keyboard or form part of a numeric keypad located adjacent to the keyboard. The cursor control device may be a speed aid but the hand(s) must be removed from favored reference keys on the keyboard to use such as a control. Although it would be advantageous to have the cursor device in continuous contact with the operator, all fingers are usually already committed to keyboard contact.
Small Instrument Manipulation and Small Part Assembly
Consider a simple generic and repetitive task of picking up a delicate object with a forceps at one location and depositing it in a proper orientation at a new location. An arm rest to aid the hand would be desirable at two locations (the object, source, and final destination) but even then the arm would have to transport between these supports and guard against too forceful an impact with the second site. Again static supports may create erratic effects of friction against the skin. Perhaps the second site of deposit might be also moving on a slow assembly line or the assembly process could be enhanced by such movement. Additionally, other variations could entail more than one source site for acquiring special parts or multiple deposit sites. To address these assembly problems, two or more arm rests could be of benefit even disregarding the act of moving between sites. Rather than a multiplicity of static supports, a moving support would be beneficial, including a support which eliminates the requirement of multiple landing impacts.
Even disregarding direct hand assembly of small parts, the operation of such, that arm fatigue occurs while remaining at one or more switch sites on diverse arrangements, the operator may benefit from arm support especially if the switches require constant adjustment for various processes.
In these applications, each has a distinct range of worksurfaces or panel arrangements but they have a common need for aid to hand function by means of arm support. The arm support should cater to various demands on the operator including; ongoing use at a dominant location or control, non-use of the hand but maintaining a ready position at a favored location, and support during transfer and landing at new locations.
Foot and Ankle Function Aided by Leg Support
Generally, a foot operates a control rather than directly manipulating an object, such as in part assembly. In common practice, the leg is supported by the heel and the control is affected by both ankle and foot motion. When more than one control is addressed or there is need to modify pressure on a single variable control, then tension in the leg and the muscles of the abdomen and lower back may be required. Support at the lower leg would provide benefits analogous to arm support for hand functions. Because leg mass and muscle groups are primarily used for body transport, the effort to elevate the weight of a leg for protracted tasks is perhaps more unusual and distracting to the effort of coordinating foot and ankle functions than the act of reaching with the arm for hand functions. Sometimes, foot controls may be useful in situations where the operator must be relatively supine, prone, or reclining on the side such that differing muscle groups must contend with a disadvantageous support of the extended leg. Since foot controls are often used on heavy machinery, issues of fatigue and accident prevention are at stake rather than the issue of keyboard error.
Operations Affected by Motion and Gravity
Gravity can produce fatigue, as discussed; and predictable motion, such as that of an assembly line, can create new functional demands. However, when the whole environment of the operation is affected by motion, such as operation onboard any type of vehicle, then shifting relationships of the vehicle and a work surface, keyboard, or instrument panel can occur with respect to the operator who has an independent inertia. A seat belt merely constrains an operator's main body to these changes. An outreached limb performing tasks also experiences inertial shifts and could benefit from a limb support which at least partially imparts motion to the limb that approximates the motion of the fixed work items which are onboard.
To compensate for sudden downward shifts, a seated operator in motion can maintain a constant downward pressure on a support and with training an unconscious compensation is in place to follow sudden down shifts of reduced G force. However, such constant downward reference would increase the friction against any static support and use against an arm or leg surface. Uplift, which reresents increased G force, and some amount of side to side force can be imparted to an arm or a leg by way of the support which is fixed to the moving craft. If uplifts are constant to significant levels of G force, then fatigue may become a major obstacle to effective limb operations which can be compensated by support. In vehicles with complex manual vehicle control systems, or complex procedures carried on for other than vehicle control, operator limb support may be desirable with the same concerns for range and continuity of contact as previously described.
Handicapped Operator Aids
An inadequacy of strength in some muscle groups of a given limb in use may affect the accuracy and endurance of an otherwise achievable distal hand or foot function. This situation could be caused by birth defect, direct injury, neurologic events, and also a unique class of proximal muscular dystrophies. Again, the issues of continuous proprioceptive contact with support over a range of locations are pertinent. Incorporation of a convenient data acquisition or control device, such as cursor movement, directly into the support may be of even more value to the handicapped operator. Furthermore, having a support which eliminates friction against fixed surfaces and which allows for continual support during movement between sides would be desirable.
Safety
A basic method of safety control of machines is to provide safety zones to which the hands or feet must be placed to activate the machine controls. These safe zones are another movement in the work process and the switches at the safe zones are another target of manipulation. In a process such as assembly that requires arm movement at a vulnerable location, it may be beneficial to have a movable arm support both to move the support from the area of machine action along with the appendage and to guide the appendage to the safe zones and site of machine control. There is also a need to provide zones of safety for users of potentially dangerous equipment which provides for machine activation without danger to the limbs.